Known in the present state of the art is a device for automatic balancing of grinding wheels (cf. SU,A, No. 381941) mounted on the spindle of a grinding machine, said device comprising an unbalance transducer, an unbalance correction mechanism controlled by the aforesaid transducer and provided with four chambers spaced equidistantly along the rotor perimeter and partly filled with a fluid. Each pair of the diametrically opposite chambers intercommunicates through a passage and is connected to acompressed air source through a distributor unit incorporating an electric drive and flow-regulating valves. To correct grinding wheel unbalance, fluid is conveyed, by virtue of compressed-air pressure, from one chamber into another until the electric drive of the distributor unit is switched off.
However, the device discussed above is too sophisticated in manufacture. Besides, it suffers from an inadequate degree of automation, which affects adversely its operating reliability.
One more prior-art device for automatic balancing of grinding wheel (cf. SU, A, 619814) mounted on the spindle of a grinder is known to comprise an unbalance correction mechanism which is in fact a cylinder-shaped housing set on the grinder's spindle and subdivided into compartments or chambers spaced equidistantly therein along its periphery, and a distributor unit shaped as a plurality of air-piloted hydraulic valves arranged in the correction mechanism opposite to the chambers thereof. The distributor unit communicates, via passages, with the sources of fluid and compressed air through an adapter mechanism which is to communicate the rotatable fluid and air admission passages or ducts with the stationary sources of fluid and air. The hydraulic valves of the distributor unit are connected to their respective unbalance transducers which are in effect air-operated. The nozzles of the unbalance transducers are located in the housing of the correction mechanism, while a ring-shaped flap common to all transducers, is mounted on the grinder base.
It is a due to out-of-balance mass of the grinding wheel, that is, its unbalance, that the spindle axis is urged by the centrifugal force to displace towards the unbalanced wheel side, thus changing the clearance between the flap outer surface and the unbalance transducer nozzles, which in turn increases or decreases the pressure effective in the compressed air admission passage, which pressure actuates the air drive of a respective hydraulic valve so that the latter either opens or closes, thereby controlling the rate of fluid flow to the chamber involved.
However, such a construction arrangement of the aforediscussed known device is too sophisticated, since it necessitates compressed air admission to the rotatable housing to control distribution and supply of fluid to the chambers of the correction mechanism, which affects adversely the operating reliability of the device.
In addition, the presence of a grinding wheel unbalance which is to be corrected, is judged by the amount of displacement of the axis of spindle rotation from its geometrical axis, said displacement being caused by a centrifugal force resulting from rotation of out-of-balance masses of the grinding wheel. Such a displacement or offset effective in modern grinders is a rule of the order of 0.2 .mu.m. However, the values of the aforesaid order lie out of the zone of tolerance for the mating components of the nozzles and flap of the unbalance transducer, on which account the sensitivity of the unbalance transducer fails to meet the requirements imposed upon the accuracy of measurement of the amounts of the spindle geometrical axis offset from the axis of spindle rotation, which also affects badly the reliability of balancing.